Optical accessories for use in combination with spectacles exist for a wide variety of reasons. Sunglass type accessories, for instance, generally permit optimum use of the spectacles under varying lighting conditions. Other optical accessories provide, for example, eye shielding and vision correcting functions.
A number of factors are considered important in constructing such accessories. In this regard, it is desirable to have the optical elements of the accessory positioned in correct superposed relationship to the optical members of spectacles for proper usage and convenience. In many instances, it is highly desirable to avoid unnecessary movement of the accessory relative to the spectacle frame assembly. Moreover, facilitating quick, easy and reliable mounting and demounting of the accessory are of practical importance. Significantly, it is desirable to have these mounting arrangements as aesthetic as possible. Unaesthetic mounting arrangements, of course, detract appreciably from the commercial appeal of such accessories. Furthermore, in the highly competitive spectacle accessory field, need exists to provide the foregoing features as simply, economically and efficiently as possible.
One particular kind of optical accessory is the flip-type. It allows the user to selectively flip the shades up or down relative to the spectacle lenses. Flip-type accessories are popular for a wide variety of reasons including, of course, versatility insofar as one can quickly and easily choose whether sun shading functions are desired or not.
Mounting arrangements for releasably attaching optical accessories to spectacle frames are significant components of the accessories as well as, of course, the manner by which the shades are pivoted. In this latter regard it is highly desirable to obtain the pivoting motion without disrupting the stability of the accessory. The following are exemplary of prior art optical accessories and their releasable mounting arrangements: 3,413,057; 3,555,563; 3,741,634, and 4,176,921.
Known optical accessories exhibit a number of deficiencies in connection with the foregoing enumerated factors. For example, most accessories must have specially constructed frames to be attached to. Hence, such accessories are not compatible with many kinds of existing prescription glass frames.